OPINION:
Prime Minister John Key deserves praise for building on his one-election tradition of giving voters plenty of notice — in this case more than six months – of polling day.

His choice of September 20 was one of only a handful of available dates that did not clash with a big sporting event or disturb the school holidays.

Waiting until November, when the G20 summit in Brisbane could see plenty of world leaders add this country to their itinerary was not an option though it looks as if United States President Barack Obama will not be one of them.

But going relatively early is more than a little convenient for Key and National too.

It lessens any complications from ACT MP John Banks losing his court case and being forced out of the House, which would rob National of the deciding vote on centre-Right laws it wanted to pass.

Key made the announcement with Labour at a low ebb in the polls and with morale hit by leader David Cunliffe’s recent woes.

But as Key noted, an election – like a World Cup rugby crown – can look easy on paper but prove hard to carry off once the teams hit the field.

The longer he waited, the more likely Labour would get its act together, an unexpected problem would blindside him ... or drip-fed interest rate rises would erode confidence in mortgage-land.

The election announcement also gives him a platform, starting later today, to discuss changing the flag. He spruiked his speech at Victoria University as being ‘‘thorough and thoughtful’’ – which hardly suggests he has changed his mind and will dump the whole idea.

It remains to be seen whether the first step of what should be a two or three step referendum will coincide with the election, though that seems sensible.

Either way, a debate about the flag enables Mr Key to signal he is forward-looking but cautious, without throwing the whole constitutional kit and caboodle at voters.

Labour can – and will – argue the flag is a distraction from more important matters.

But there will be some in the Opposition ranks tempted to broaden the issue into a wider constitutional debate.